This invention relates to a power unit for a motor-cycle, and, more particularly, it is concerned with a power unit for a motor-cycle of a construction, in which a power transmission case which supports at the rear end thereof the rear axle is integrally and connectively provided at one end of a crank case of a motor-cycle engine, and a starting power transmission mechanism to drive the rear axle of the motor-cycle is accommodated in the power transmission case.
It is a principal object of the present invention to provide a power unit for a motor-cycle of the above-described type, in which the power transmission case is divided into the left and right halves, a driving power transmission mechanism being disposed in one of the case halves, and a starting power transmission mechanism being disposed in the other of the case halves so that a crank shaft of the motor-cycle engine and the starting power transmission mechanism may be connected at the time of joining both case halves, thereby making it possible to assemble and disassemble the driving power transmission mechanism and the starting power transmission mechanism individually and separately, and thereby facilitating the assembly and maintenance of the power unit as a whole.
It is another object of the present invention to provide a power unit for a motor-cycle of the above-described type, which is easy in the starting operation and is high in its durability, and in which a certain definite force is accumulated in a spiral spring by swing motions of a pedal shaft, with the accumulated spring force of which cranking of the motor-cycle is performed, then, by restricting the winding quantity and the unwinding quantity of the spiral spring with the aid of a buffer member provided on the power unit, any excessive winding action to, impact due to the release onto, or breakage due to reverse rotation of, the spiral spring as well as separation of its tip end parts from their fixing member can be prevented.
According to the present invention, briefly stated, there is provided a power unit for a motor-cycle of a type having a power transmission case which supports at the rear end thereof a rear axle and which is integrally joined together at one end of a crank case of an engine, wherein the power transmission case is constituted with an inner half directly connected to the crank case and an outer half to be separably connected to the inner half, the rear axle is fitted onto the inner half of the power transmission case, and, at the same time, a driving power transmission mechanism is disposed in the inner half to connect the rear axle and a crank shaft of the engine, a pedal shaft having an engine starting pedal connected at one end thereof and an engine starting shaft adjacent to the crank shaft on the same axis is fitted onto the outer half of the power transmission case, and, at the same time, a starting power transmission mechanism is disposed in the outer half to connect the crank shaft and the engine starting shaft, and a driving member and a driven member of an over-running clutch for starting which are engaged each other at the time of coupling of the inner and outer halves of the power transmission case is provided at the opposing ends of each of the starting shaft and the crank shaft.
There has thus been outlined, rather broadly, the more important features of the present invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention. It is important, therefore, that the claims be regarded as including such equivalent construction as do not depart from the spirit and scope of the invention.